Generally, when a scanning module (e.g., a scanner of computer peripheral or a multi-functional printer used in the office or home) is used for scanning, the initial magnification is controlled by the design of a camera lens in the scanning module. In other words, when a document is placed on the scanning module for scanning, a light source projects light onto the document, and a reflective mirror set in the scanning module receives light from the document. The light is then reflected to the camera lens and focused onto a photosensitive component, which converts analog optical signals into digital signals representing an image to finish scanning and conversion of the whole document image.
However, there is inevitably inaccuracy in the magnification of the above camera lens. Moreover, the total optical length between the document and the photosensitive component may change due to inaccuracy in the arranged position of the reflective mirror set in the scanning module. Therefore, the scanning quality of the document cannot be effectively controlled, and the quality of the final output image is affected.
Accordingly, the above conventional scanning module has inconvenience and drawbacks in practical use. The present invention aims to resolve the problems in the prior art.